Possibility of artificial sweeteners as chemical tracers for estimating groundwater flow systems and anthropogenic implications in Kumamoto area

In recently years, large amounts of low-calorie sweeteners have been used in a wide variety of soft drinks and foodstuffs in the world. These compounds are less degradable during wastewater treatment process, and are detected in the aquatic environment in European countries. Our previous studies reported the occurrence and concentrations of artificial sweeteners in wastewater treatment plants (WWTPs) in Japan. In addition, these compounds were detected in a spring water sample, which imply the occurrence of artificial sweeteners in groundwater. Since groundwater has been used as drinking water in Kumamoto, conservation of groundwater and safety management of its flow systems are of great concerns in this city. In this study, we analyzed artificial sweeteners in 135 groundwater samples collected from both observation wells and water supply wells. As a result of analysis, three artificial sweeteners, acesulfame, sucralose and saccharin were detected in groundwater samples, at geometric mean concentrations of 0.73 ng/L, 20 ng/L and 0.40 ng/L, respectively. Acesulfame showed high detection frequency among three sweeteners analyzed, suggesting its extensive distribution in groundwater in Kumamoto region. High concentration of acesulfame was detected in groundwater samples collected from wells located nearby recharges area of river water into groundwater. The concentrations of acesulfame decreased with the increasing of distance along to the general groundwater flow, which was reported previously. These results imply the possibility of artificial sweeteners as chemical tracer for understanding the groundwater flow systems. The high concentrations of acesulfame and sucralose were detected in several wells around urbanized area of Kumamoto. This may suggest the potential effect of leaking wastewater into groundwater by a break of sewer pipeline networks.